Fruit pulp fibers contain pectin and cellulosic materials such as hemicellulose. Pectin is present in the cell walls of all plant material and functions, in combination with cellulosic material, as an intercellular cementing material. The main component of pectin is a linear D-galacturonan, many of the carboxyl groups of which are esterified with methanol. Other components include L-arabinan and D-galactan which together may form up to 20% by weight of the pectin. The main raw materials for pectin and hemicellulose are the peel of citrus fruits such as lemon, lime, orange and grapefruit, as well as apple pomace which is the residue remaining after pressing of apple to obtain apple juice.